void f1(t a);
void f2(t &a);

int main(){
  t a; //create a variable of type t;
  f1(a);//pass the value of a to the function f1
  f2(&a);//pass the address of a to the function f2 but, this function has a reference as a parameter so it shouldn't compile, you should pass the variable f2(a)
  f1(&a); // pass the address of a to the function f1, so f1 should contain a pointer as a parameter, but that's not the case, so it won't compile
  f2(a); //passing by reference to the function f2
}

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